Method afterOp

src/KeyPromiseQueue.js:32–42

(key)

  }

  afterOp(key) {
    const tuple = this.queue[key];
    if (!tuple) {
      return;
    }
    tuple[0]--;
    if (tuple[0] <= 0) {
      delete this.queue[key];
      return;
    }
  }
}